Ten minutes into Lieutenant Colonel Matt J. Martin's first mission as a Predator drone pilot, he marked a target in Baghdad for a "Spooky" gunship.

And then it opened fire.

"Death from above. Poor bastards down there in the windows never knew what hit them," he wrote in a 2010 book.

As he stood up to stretch in a trailer at Creech Air Force Base near Las Vegas, he remembered that his wife had asked him to buy some milk on his way home.

Lieutenant Colonel Martin was one of the US military's first "combat commuters".

These virtual top guns serve on the frontline of the United States' international military operations - but from trailers in the middle of the Nevada desert.

Drone (Unmanned Aerial Vehicle (UAV)) pilots are centre to the foreign policy objectives of the US President, with Barack Obama personally signing off the use of drone strikes to take out terrorists*.

'LONG DISTANCE WARRIORS'

So who are these pilots who carry out the President's commands?

On the surface, their lives aren't that different from the average office worker.

"[We] commute to work in rush-hour traffic, slip into a seat in front of a bank of computers, 'fly' a warplane to shoot missiles at an enemy thousands of miles away, and then pick up the kids from school or a gallon of milk at the grocery store in his way home for dinner," wrote Lieutenant Colonel Martin in the book Predator: The Remote-Control Air War over Iraq and Afghanistan: A Pilot's Story about his time flying drone missions over Iraq and Afghanistan.

"Sometimes I felt like God hurling thunderbolts from afar."

Associate Professor Missy Cummings, one of the US Air Force's first female fighter pilots and an expert on these "long-distance warriors", told smh.com.au their experiences were "surreal at best".

"When I used to fly missions, you would come back and you would be in that environment 24/7.

"In the UAV missions, you might fly these missions and you might launch weapons and kill someone and there is a debriefing that you go through ... But you are home much sooner than you would [usually] be."

Drone pilots mostly operate out of Air Force and Army bases in the US - and also from the Central Intelligence Agency's headquarters at Langley, Virginia.

They are briefed about their missions, then sit together with a sensor operator - who operates the drone cameras - for a 12-hour shift, watching a multitude of screens and holding joysticks modelled after PlayStation controllers**.

Most of the time, they are monitoring targets or compounds. But sometimes, they also take out targets.

In the early days of the program in the mid-2000s, all pilots previously flew fighters or bombers. But as the demand for drones grew exponentially, there weren't enough existing combat pilots to fill the roles***, Associate Professor Cummings said.

To meet the need, the Air Force began to roll out a new recruitment and training program tailored for UAV pilots.

The Air Force now trains more drone pilots than F-16 pilots and expect their numbers to hit 1100 in the next year or two, Air Force Magazine reported.

POST-TRAUMATIC STRESS DISORDER

But the constant demand for more drone missions has taken a toll on the overstretched pilots. An Air Force study found that just under one-third of active duty drone pilots reported symptoms of burnout and 17 per cent of them reported "clinical distress" - the point when their work and personal lives are affected by stress, Reuters reported.

Their main source of stress was long hours and lack of staff. Combat stress was another issue.

Some pilots experienced "existential conflict", a "guilt feeling, perhaps - or a 'Did I make the right decision? Was this a friendly fire incident? Was it a good outcome? Was it a bad outcome? Could I have done it better?'" Colondel Hernando Ortega, a surgeon for the Air Force's Intelligence, Surveillance and Reconnaissance Agency, told The Christian Science Monitor.

"We have guys who have not deployed anywhere and yet can still have combat effects of distance places."

The long hours watching screens has also thrown up another potential problem - boredom.

"You can watch a wall of screens and nothing will be happening. You could be waiting for something to move. Waiting, waiting, waiting. So it can actually be excruciatingly boring," said Associate Professor Cummings.

'FUTURE OF MODERN WARFARE'

When Lieutenant Colonel Martin came face to face for the first time with a drone during his orientation at Creech Air Force Base, an Air Force Lieutenant Colonel told him: "Gentlemen, what you are looking at is the future of modern warfare."

Drones are now used throughout US military operations.

There are regular news stories about strikes in Pakistan, Afghanistan and Yemen - but also growing fears about how these strikes, sometimes called targeted killings, are accountable and if they conform to international law norms.

There have also been various attempts to document how many people have been killed, including civilians, by the strikes, and if they are as clinical as their advocates claim.

Drones are also getting smaller - and becoming part of civilian use. In Australia, Victorian police are trialling the use of drones, following the lead of their American law enforcement counterparts.

"This is much beyond an evolution. It's a revolution," military expert Peter Singer told De Spiegel magazine.

**A military robotics researcher told the author of Wired for War, Peter Singer, that the controllers were "modelled ... after the PlayStation because that's what these 18, 19-year-old Marines have been playing with pretty much all of their lives".

***The Air Force had about 350 drone pilots as of December 2011, Reuters reported. In 2007, the Air Force flew 10 to 15 Combat Air Patrols (CAP) each day. Last year, more than 60 CAPs were flown in the same time period. And the military has set a new target of 65 patrols by 2013 - marking a 1200 per cent growth in operations since the Afghan war started in 2001, Air Force Magazine, the online journal of the Air Force Association, said. "We're in the process of standing up a completely new career field now," Major General James A. Whitmore, the Air Force's Air Education and Training Command director of intelligence, operations, and nuclear integration told the magazine.